Rainbow would get a Mustang
Applejack would get a Chevy Pickup
Fluttershy wouldn't drive because it's scary
Rarity would drive a vespa
Twilight Sparkle would use a Honda Civic
Pinkie would get a generic party bus or a VW Bug

Spike would drive a bike because he's too young to get a driver's license. And he would have training wheels because he falls all the time. The bike would have a wicker basket for all of Twilight's stuff.